Torquemeter and control means



Jan. 26, 1960 R. D. TYLER ETAL 2,922,931

TORQUEMETER AND CONTROL MEANS Original Filed June 29, 1951 3Sheets-Sheet 1 Jan. 26, 1960 R. D. TYLER ETAL TORQUEMETER AND coNTRoLMEANS 1951 5 Sheets-Sheet 2 Original Filed June 29,

F u i m! 1 "lu 3nventors Bu c/Bfz'zz 7 f ac/22055 w ttorneg Jan. 26,1960 R. D. TYLER ET AL TORQUEMETER AND CONTROL MEANS Original Filed June29. 1951 3 Sheets-Sheet 3 'N illlH Snventou Jzzsseffa @3274 1 E(Ittorneg United States Patent O TORQUEMETER AND CONTROL MEANS RussellD. Tyler and John M. Whitmore, Indianapolis, Ind., assignors to GeneralMotors Corporation, De-

troit, Mich., a corporation of Delaware Original application June 29,1951, Serial No. 234,308, now Patent No. 2,766,617, dated October 16,1956. Divided and this application September 25, 1956, Serial No.612,027

3 Claims, (Cl. 317-149) This invention relates to an electronictorquemeter and control means operated thereby.

Y This application is a division of Serial No. 234,308 entitledTorquemeten filed June 29, 1951, now Patent No. 2,766,617.

One feature of the invention is that it provides an improvedtorquemeter; another feature of the invention is that it provides atorquemeter comprising torque transmitting means, means for developingtorque and reference electrical signals differing in phase as a functionof the amount of torque transmitted, and means for measuring said phasedifference; a further feature of the -invention is that it includesphase detecting means connected to the signal developing means forproviding pulses which vary quantitatively as a function of the phasedifference between the torque and reference signals; still anotherfeature of the invention is that the phase detecting means includes anelectronic switch operated `by the torque and reference signals; yet afurther feature of the invention is that it eliminates possibility oferror due to misalignment of the torque developing means which include arotatable torque shaft and a reference shaft coaxial therewith andrigidly connected thereto at one end and freely rotatable relativethereto at the other end; lyet another feature of the invention is thatsaid shafts are concentric and have pickup means associated therewithadjacent the free end of the reference shaft; still -a further featureof the invention is that a vibration damper is mounted on the referenceshaft to dampen vibrations at the resonance point of the shafts as thespeed yof rotation of the shafts varies between zero and operat- Iingspeed; an additional feature of the invention is that `voltage pulsesare provided having a time duration pro- ;portional to the phasedifference between the torque and reference signals, and switch meansoperable `by voltage 'pulses of a predetermined time duration areprovided to give an indication of power failure; and still a further"feature of the invention is that it provides torque responsive controlmeans for feathering or declutching 'the propeller of an aircraft.

Other features and advantages of the invention will be apparent from thefollowing description and from the tdrawings, in which:

Figure 1 is a schematic diagram of a dual power aircraft propulsionplane :having the novel apparatus asso- ;c'iated therewith;

Figure 2 is a Iside elevational view of the torque transmitting meansassociated with one of the engines of Figure 1;

Figure 3 is an enlarged fragmentary longitudinal sectional view throughthe shafting of Figure 1, portions being broken away; and

Figurey 4 is a schematic diagram of the electronic 'circuits.

The novel torquemeter is particularly adapted for use in an aircraft,and according to one embodiment of the invention torque transmittingmeans are provided comprising a rotatable torque shaft connecting powermeans 2,922,931 Patented Jan. 26, 1960 being adapted to twist as afunction of the amount of torque it transmits. A reference shaft isconcentric with the torque shaft and is rigidly connected thereto at oneend, as the power end, and freely rotatable relative thereto at theother end, as the load end. The concentric arrangement of the shaftseliminates any possibility of error due to misalignment of the shaftsdue to static or dynamic loading of the supportingV frame. The torqueshaft twists in a degree proportional to the amount of torque ittransmits during operation, and electrical pickups are provided on bothshafts adjacent the free end of the reference shaft for developingtorque and reference electrical signals displaced in phase in a degreeindicative of the rotative displacement between the torque and referenceshafts at the pickup location. These signals' are applied to a phasedetecting circuit, and after being modified in shape are utilized tooperate a multivibrator or iiip-op circuit to provide pulses of constantamplitude having a time duration proportional to the phase differencebetween the torque and reference signals. Current indicating meansconnected to the multivibrator provide an indication of the averagecurrent flow through one of the multivibrator tubes, this current ilowbeing indicative of the amount of torque developed. `v

Impulses from the multivibrator may be utilized as a sensing device tooperate switch means for any desired purpose, as, for example, tofeather or de-clutch the propeller of the airplane inthe event thetorque developed by the engine drops below a predetermined level.

While the torquemeter illustrated in the drawings is particularlyadapted for use in an airplane engine and is illustrated as beingincorporated therein, it will be understood 'that the invention isequally applicable to any torquemeter wherein it is desired to indicatethe torque delivered by power means to a load.

Referring now more particularly to Figures l, 2 and 3, the referencecharacter 9 designates power means, here illustrated as an airplaneengine having a power output shaft 10, and reference characterdesignates aload,

here illustrated as a propeller connected through gears 9.1 and 92 to aload input shaft 11. A clutch illustrated diagrammatically at 93 may becontrolled through mechanical linkage 94 by a clutch actuator 95.r[he'propeller may be feathered through a propeller actuator 96 which is4coupled to the propeller through a mechanical linkage indicated at 97and the operation of the propeller as a constant speed variable pitchpropeller is directly controlled by an electric propeller governor 98which transmits signals to a hydraulic mechanism in the propeller, whichincreases and decreases pitch, through an electrical circuit indicatedat 99. The apparatus illustrated includes dual power plants, similarparts of the second power plant being designated by similar referencecharacters with a prime For more details of the power vplants referencemay be had to the application of Irwin et al., entitled Control Systemfor Turbo-Prop Engines, filed November 8, 1950, as S.N. 194,716, `andnow Patent No. 2,851,113. A torque shaft 12 is coupled at one end to theengine output shaft 10, and is coupled at the other end to the loadinput shaft 11. Adjacent the propeller or load end of torque shaft 12 isa radial flange 13 having extending radially therefrom a unirse-irlalignment measured parallel t the axis ci the shaft assembly.

When the torque shaft 12 is loaded, it willl twist or wind in4 an amountproportional to the torque it transmits, while the shaft 15 (whichtransmits no torque other` than that developed by its own inertia)Y willbe' displaced rotatably at its free end from its no-load angularl orlrotative relationship to the shaft'12., so that the exciter teeth onthe reference shaft 15 will be rotatably displaced from the exciterteeth 14 on the torque shaft 12 in an amount proportional to the torquetransmitted by the torque shaft.

Ifv the apparatus is used in a turbine type airplane engine asillustrated inFig11,re 1 the: Operating speed of rotation may be between11,590` and; 14,301),` revolutionsperj minute, and the natura-l,resonance` point of the shafting assembly will be below this frequency..In one embodimenty of the invention the shafting assemblyy had, a whipnatural resonance point at 6,000 revolutions per minute. lin order todampen the vibrationsk encountered when passing through the whip naturalresonance point during starting and stopping, a vibration damper,designated generally at 22, is provided. This damper comprises a bearing23, located. substantially at the midpoint of the shaft assembly andcarried in a bearing race mounted between the shaft 15 and a neoprenedamper 24 which is secured to a dust tube 25 (Figure 3,) `whichencompasses the shafting assembly.

Electrical signals indicative of the rotativeposition of the load end ofthe torque shaft 12, and hereinafter referred to as torque signals, aredeveloped by pickup means comprising the spaced teeth 14 on the torqueshaft and a magnetic pickup member 27 mounted closely adjacent the pathof movement of the projections 14.

Electrical signals indicative of the rotative position of the load endof the reference shaft 15, and hereinafter referred to as referencesignals, are developed by pickup means comprising they spaced teeth 20on the reference shaft and a vmagnetic pickup, member 28 .mountedclosely adjacent the path of movement of the projections 20.

One pickup member is displaced a few degrees with respect to the otheraround the circumference of the shafting assembly, but, as pointed outabove, the teeth 'on the respective shafts are Vin line under no-loadconditions. As the shafts are rotated electrical signal irnpulses areproduced each time one of the teeth passes closely adjacenty itsrespective pickup member. Since thepickups are circumferentiallydisplaced, the torque signals and reference signals willy be out ofphase a few degrees under zero load conditions. As the torque shaft-winds, as it will when load is. applied, the teeth on the torque shaftare displaced further with respect to the teeth onV the reference shaftin an Vamount proportional tothe torque transmitted. `This furtherdisplacement causesan increase in the phase difference between thetorque andreference signals.

For calibration purposes a third pickup 29 is mounted radially over thereference exciter teeth 20. This pickup `is located a fixed distancefrom the reference pickup 28 around the circumference of thereferenceshaft to provide a constant phase difference between thereference signals and the signals developed by the calibration pickup.This `fixed phase difference may be Vconsidered as; simulated torque inthe calibration ofthe `electronic circuit.

The electronic circuit for vthe torquemeter is shown .,SChematically inFigure 4, the purpose of the circuit Abeing to convert the4 electricalsignals to steep-sided voltage pulses which are used to trigger `amultivibrator circuit, one tube` of which passes current yin a quantityindicative of the phase ydifference between the 'LOITQUG and referencesignals. This phase difference is indiiv@ 4 of the amount of torquetransmitted by the torque shaft.

Referring to Figure 4, the circuit shown may be powered from aconventional battery 30, which may be the battery of the airplane. YOneterminal of the battery is connected to ground and the other terminal isconnected through the coil 31 of a relay to one contact of an On- Oifswitch k32, the other contact of which is grounded.

When theswitch 32 is manually closed the relay con-V tacts are closedand thek battery 30, is connected through the relay armature 31a to themotor element 33 of a motor-generator designated generally at 34 andhaving a generator Velement 35 for developing a high D.C.` voltage forenergizing the tubes of the electronic circuit. This voltage may beadjusted in magnitude by means of a variable resistor v36, and isfiltered Vand regulated by a filter condenser 37 and a regulatory systemcomprising voltage regulating tubes 38 and 39. A neon lamp 40 isconnected between the high voltage lead andy ground to provide a pilotlight.

The reference signals developed by the pickup member 28 (schematicallyshown in Fig. 4) are converted into steep-sided negative voltageimpulses in a circuit including a rectifier 45 and tubesl, 47 and 48.The signal from the pickup member ,28.V is rectified by the rectifierand vapplied to the signal grid of the tube 46 which maybe a pentode oftubetype No. l2AU6. The resultingimpulse in the anode, circuit of thetube 46 is differentiated by a circuit includiugacondenser-S which mayhave a value of l0 micromicrofarads and a resistor 51 which may have avalue of 2,0000-ohrns, and the differentiated pips are applied to` theinput gridA of the tube 47 which may be aA pentode of tubel type 12AU6.The pips are clipped by the tube-47,'and the resulting steep-sidednegative impulses in the anodey circuit are passed through the diode`4S. which may comprise one section of Va dual tube of type No. 12AL5.

The torque signals developed by the pickup member 29 are converted intosteep-sided negative impulses in la similar circuit including yarectifier 52 and tubes 5 3,

54 and 55. In order to select the torque signals or the calibrationsignals as desired, a manually operable calibration switch 5,6 isprovided. One COutaCt 0f this switch is connected to ground and theother contact is connected to the batteryk 30,through a relay coil 57.The armature 57a o f the relay comprises the movable pole of a singlepoledouble throw switch, the armature or movable pole being connected tothe rectifier 52 and the stationaryY contacts Abeing connectedrespectively to the pickup members 27 and 29,. When thecalibrationswitch 56 is open as illustrated, the. torque pickup member 27 isconnected in the circuit. When the vcalibration switch 56'is .closed therelay is energized, disconnecting the Vpickup member 27 yandconnectingthe calibration pickup member 29 `into the circuit. Withthe calibrationswitch open asrillustrat'ed the torque signals are amplified Vin thetube 53, differcntiatedin acircuit comprising a condenser 60 and aresistor 61, the differentiated pulses are clipped in the tube 54, andthe` resulting negative steep-sided voltage impulses are passed 4throughthe rectifier y which may comprisethe other section Yof the above`mentioned 12AL5 type tube.

The multivibrator or iiip-op circuit comprises a normally conductingtube `62 and a normally zout-off` tube 63, the respective anodes andscreen grids of these tubes being interconnected by means of leads 64and 65. In the normal condition of the circuit, tubev 62 is conductingand the anode voltage of this tube (and hence the screen voltage of'tube 63) will be relatively low. This low voltageholds tube 63 cut off.

e Whe'nithe steep-sided negative reference impulse is applied tothecontrol grid of tube 62 this tube is instantaneously cut off, raisingthe anode voltage of tube 62 yand the screen grid voltage of tubeV 63,`so that tube 63 now becomes conductive and current ows through amilliameter 66 which is connected in the cathode circuit of 'las M tube63. Tube 63 passes a constant current dependent upon the tubecharacteristics and the applied voltages. Tube 63 remains conductiveduring the phaseditference period between the reference and torqueimpulses. Upon the occurence of the succeeding negative torque impulse(which impulse is delayed in phase because of the positoning of thepickup member 27 and because of the windup or twist of torque shaft 12under load) tube 63 is cut off. At the instant tube 63 is cut off itsanode voltage, and the screen grid voltage of tube 62, becomes morepositive so that tube 62 again conducts, and its lowered anode voltagenow holds tube 63 in cut oi condition.

Consequently, it will be seen that the above described phase detectingcircuit provides current pulses which Vary quantitatively as a functionof a phase difference between the reference and torque signals, and thecurrent measuring meter in the cathode circuit of the tube 63 providesan average indication of the amount of current flowing through tube 63.This meter may be calibrated directly in terms of torque.

Obviously, the accuracy of the indication depends upon the constantcurrent characteristics of tube 63, and if the amplitude of the currentflowing through the tube varies, the reading will be inaccurate. Inorder to check the accuracy of the indication it 1s merely necessary toclose developed from the reference shaft 15, these signals maintain apredetermined phase difference. With the calibration signals connectedinto the circuit a variable resistor 68 may be adjusted to vary theanode and screen voltages on the tubes 62 and 63 to provide propercalibration.

ceases to deliver power in order to eliminate quickly the drag caused byrotating the propeller and engine by air By using the torquemeter as asensing device, it is possible to feather or de-clutch the propellerautomatically when the engine torque falls below any predeterminedpoint.

'A circuit for accomplishing .automatic feathering or declutching isshown in -Figure 4. A lead 70 is connected between the anode of tube 63and a condenser 71, the other termmal of the condenser being connectedby means the cathode of a diode 73. A resistor 73a anode of the diode 73and to ground. The anode of the triode 76 is connected to the B-plussupply through the coil 78 of a relay, and the cathode of said triode isconnected to ground through a resistor 79. Another triode 80 has itscathode connected to ground in a common circuit through said resistor79, and its anode connected to the B-plus supply through a resistor 81.A resistor 82, a potentiometer 83 and a resistor 84 are connected inseries between the anode of tube 76 and ground, and the of the relayforms a normally open switch which may be in the circuit controlling thefeathering or de-clutching relay for the aircraft propeller asdisclosed, for example, in application S.N. 194,716.

The operation of the automatic feathering or de-clutching circuit is asfollows: During each conductive interval of tube 63 the anode voltage ofsaid tube will be in the of the amount of torque developed by theengine. This negative voltage impulse is passed through the condenser71, and the diode 73 and resistor 73a which is connected thereacross toprovide a clamping or D.C. restoring action circuit to maintain the so'nThis voltage s utilized to control the operation of switch 78a. Acathode voltage for tubes 76 and 80 is developed across resistor 79 bythe ilow of current through said tubes, and this voltage provides a biasvoltage for the tubes. Current flowing from the anode of tube 76 throughresistors 82, 83 and 84 to ground also develops a voltage at the grid oftube 80.

The circuit is so designed that above a predetermined ercentage of ratedengine power the voltage at point than the cathode voltage of tube 76.In the event engine power is reduced the torque transmitted by shaft 12deconsequent closure of armature 78a, closing the circuit to theautomatic feathering or de-clutching relay in the propeller controlcircuit so that the propeller is automatically feathered or de-clutched.

The circuit includes several safety features.

properly condenser 71 will block the D.C. anode voltage of tube 63 andthe grid voltage of tube 76 will return to zer leaving tube 76 cut offand the automatic the respective fila- 80 are connected leaving theautomatic circuit open.

In the event of engine failure in a turbo prop aircraft engine, thepropeller would drive the engine, developing substantial negative torqueand creating a very unde- In the event of power failure during atake-off it is important that the propeller be feathered (in amulti-engine aircraft) or de-clutched (in a single engine aircraft) assoon as possible. The

so arrangedr that the relay contacts 78a will be closed in the eventpower falls near zero, or even in the event negative torque isdeveloped, .in order to feather or declutch the propeller at all timesWhen-the enginer fails or is throttled down.

While We have shown and described one embodiment of our invention, it issubject to many modifications. Changes, therefore, in the constructionand arrangement may be made without departing from the spirit and scopeof the invention as set forth in the appended claims.

We claim: l

1. Electronic control means of thecharacter described, including: aiirst tube having anode, cathode and grid elements; circuit meansproviding a current path between said anode and cathode;V currentoperated switch means connected in said current path', a second tubehaving anode, cathode and grid elements); circuit means common to bothtubes for providingl a bias voltage for both tubes when either tube isconducting; circuit connections between the anode of said rst tube andthe grid of said second tube for developing a voltage'to cut off saidsecond tube when said rst tube is conducting; pulse generating means fordeveloping control voltage pulsesv of one polarity which vary in time,duration as a direct function of variations in the control operation;pulse restoring means connected with the generating means for developingmodied control voltage pulses ofthe other polarity Which Vary in timeduration as an inverse function of the variations .in the controloperation, means for integrating said modied control voltageV pulses toprovide an average control voltage which varies in magnitude as aninverse function of variations in said'control operation; and circuitmeans for applying said average control voltage to the grid of one ofsaid tubes to control the conductivity of-said firsty tube.

2. Electronic control means of thecharacter described, including: afirst tube having anode, cathode and grid elements; current operatedelectromagnetic switch means connected to the anode of said tube;arsecond tube having anode, cathode and grid elements; circuit meanscommon to the cathodes of `both tubes for providing a bias voltage forboth tubes when either tube is conducting; circuit connections betweenthe anode of said first tube and the grid of said second tube fordeveloping a voltage to cut off said second tube when said iirst tube isconducting', pulse generating` means .for developing negative controlvoltagepulseswhichv-ary in time dura,- tion asta direct function ofvariations "in a ycontrol operation; a circuit forrestoringthe directcurrent component of said pulses toxa predetermined level for providingpositive control voltages which'vary in time duration as an inversefunction of the variations in the control operation; meansforintegrating saidl positive pulses to provide an average controlvoltage which varies in magnitude as a function ofivariations in saidcontrol operation; and circuit means for applying said average controlvoltage to the grid of said first tube to controlthe conductivity ofsaid first vtube as an inverse function of variations in said controloperation.

3. A control circuit responsive to a predetermined value of aconditioncomprising control voltage generating meansy including armultivibrator for developing negative control voltage pulses which varyin pulse duration as a direct function of variations in said condition,a pulse restoring circuit includingy a series condenser and diodeconnected across one tube of said multivibrator, a resistor across saidydiode for developing positive con-4 trol voltage pulses which vary intime duration as an inverse function of the variations in saidcondition, an integrating circuit connected across said resistor, and anelectronic switching circuit connected across the integrating circuitand including a current operated relay r'for providnga control operationwhen said condition attains apredetermined value.

References Cited in the le of this patent UNITED STATESA PATENIS YOTHERREFERENCES E.M.L. Laboratories Electronic Switchingi:V ElectronicEngineering, September 1947, p. 2.82.

